For many years it has been the common practice in angiographic and cardiovascular procedures to use various angiographic catheters having different distal tip shapes in order to perform various angiographic studies. For example, when performing coronary angiography, it is common to perform studies of the left coronary artery, the right coronary artery, and the left ventricle by injecting X-ray opaque contrast liquid into each of the right and left coronary arteries and also into the left ventricle. Each injection is done with a separate catheter having a specially formed distal tip adapted to facilitate entry into the ostium of the right or left coronary artery. Typically, a catheter having a pigtail shape is used for left ventricular studies. In order to perform these studies it has been the typical practice to exchange catheters for each study. That is time consuming and subjects the patient to the trauma of multiple catheter insertion and removal. Additionally, the use of multiple catheters increases the risk of a blood clots and, in general, presents greater risk for complications.
The desirability of reducing the time involved in performing such angiographic studies as well as minimizing trauma to the patient by making a catheter having a tip shape adjustable while in the patient has been suggested in the prior art. U.S. Pat. No. 4,033,331 to Guss discloses a specially formed catheter having two lumens, including a main lumen through which the radiopaque contrast liquid may be injected into the blood vessel and another lumen which receives a relatively stiff elongated contour wire. The distal end of the catheter has a predetermined curved shape which can be progressively straightened by advancing the contour wire distally through its lumen. The system discussed in the Guss patent has several disadvantages, the principal one being that it cannot be used with a conventional angiographic catheter. The practice of the technique disclosed in the Guss patent requires the use of the special two lumen catheter construction. That catheter construction necessarily has reduced flow area in the main lumen because of the necessity of providing the cross-sectional area for the contour wire lumen. Because it is important to maintain as large a flow area as possible in an angiographic catheter so that the radiopaque contrast liquid can be injected at a relatively high flow rate. The two lumen catheter construction comprises that desirable feature.